Thermodynamic reciprocating apparatus



Jan. 14, 1964 F. DANIELS ETAL 3,117,414

THERMODYNAMIC RECIPROCATING APPARATUS Filed July 14, 1961 2 Sheets-Sheet 1 TRANSPARENT CYLINDER HEAD I3 IO 3 w 5; WI 1m 31:: Q1! 0 w 1 3 II INVENTORS 4 FARRINGTON DANIELS THEODOR FINKELSTEIN ATTORNEY J n- 1 1964 F. DANIELS ETAL THERMODYNAMIC RECIPROCATING APPARATUS 2 Sheets-Sheet 2 Filed July 14. 1961 TRANS'PARENT CYLINDER HEAD H RADIANT ENERGY ABSORBING MATERIAL INVENTORS FARRINGTON DANIELS THEODOR FlNKELSTElN /%ww4 c/ZU ATTORNEY United States Patent "ice 3,il7,-t-l4 THERMSDYNAMEC RECEPRGCATKNG APPARATUS Farrington Daniels, Madison, l -Ila, and Theodor Finkelstein, Columbus, Ulric, assignors to Wisconsin Alumni Research Foundation, Madison, Wis., a corporation of Wisconsin Filed July 14, P961, Ser. No. 124,698 Claims. (Cl. 69-24) This invention relates to an improvement in thermodynamic reciprocating heat engines of the regenerative type.

More particularly, this invention relates to an improvement in thermodynamic reciprocating heat engines which operate on the Stirling cycle.

Still more particularly, this invention relates to an improvement in Stirling cycle engines which depend upon radiant energy for their heat source.

Hot-gas engines employing the closed Stirling cycle have been known for many years. In recent years, attention to both the Rankine and Stirling cycle engines as energy converters has received impetus because of their potential application for space power systems where the energy source is solar. Thermomechanical systems employing solar energy as the externally applied heat sourc and utilizing the Stirling cycle were suggested as early as 1862 by John Ericcson in his publication Contributions to the Centennial Exhibition, 1876, in Chapter 45, p. 558577, entitle Sun Power-The Solar Engine, and illustrated in Plate 67.

More recent developments of the Stirling engine for application as an energy converter space power systems are fully described in publications of the American Rocket SocietyW'elsh, H. Vi, Pose, E. A., and Viright, R. B., The Advanced Stirling Engine for Space Power, ARS 1Q3349 (November 1959), and Parker, M. D., and Smith, C. L, Stirling Engine Development for Space Power, the disclosures of which are incorporated herein by reference.

In order that the invention can be more readily understood it will be more fully described in reference to the drawings in which:

FIGURE 1, is a vertical cross-sectional view of a diagrammatic representation of a hot-gas (Stirling cycle) reciprocating engine which is constructed in accordance with the teachings of the known art; and

FIGURE 2 is a vertical cross-sectional view or" a diagrammatic representation of the upper portion of a thermodynamic reciprocating heat engine which is constructed in accordance with one embodiment of the present invention.

FIGURE 3 is a schematic representation of a crosssectional view of a reciprocating hot-gas engine of the -type where one segment of the V defines a cold space and the other segment defmes the hot space and where the two segments are joined by a housing member conta. ng a regenerator, cooling means, and a secondary radiant energy-absorbing means in association with the hot space of the engine and a radiant energy-transparent closure means.

FlGURE 4 is a schematic representation of a vertical cross-sectional view of a two-piston thermodynamic heat engine with inclined cylinders and wherein a secondary radiant energy-absorbing means is afiixed to one piston head.

FIGURE 5 is a schematic representation of a vertical cross-sectional view or" the upper portion or" a reciprocating thermodynamic heat engine wherein secondary radiant energy-absorbing means is afilxed to the displacer piston.

FEGURE 6 is a vertical crosssectional view of a ther- BJHAM Patented Jan. 14, 1964 modynamic reciprocating heat engine having a doubleacting combination of numbers of pistons in adjacent cylinders.

Referring to the figures, in which identical reference numerals indicate identical elements, a displacer 2 is adapted to reciprocate in cylinder 1. The space above displacer 2 is the hot space 3 of the hot-gas engine. The working medium (usually a pure gas in the Stirling engine cycle) flows between the cold space 4, the volume of which is determined by piston 5, and the displacer 2, and the hot space 3 through a cooler 6 (fin-type cooling may be used as is shown at 15 in the schematic representations of FIGURES 4 and 6) a regenerator 7 and a heater 8. Heater 8 has been depicted schematically only, Various mechanical arrangements being usable depending upon the energy input means. (Various adaptations are shown in US. Patents Numbers 2,621,474, 2,618,923, and 2,616,- 250.) In all of these the engine head 9 is exposed to some heating means which can be radiant energy as shown in the works of John Ericcson referred to hereinbefore. Many previous hot-gas reciprocating engines required that the motivating energy be transmitted to the interior of the engine solely through the engine head. This was an obvious disadvantage and adversely aflected the efiiciency of the engine since it was necessary to transfer the heat generated outside the engine head through the head itself and, more importantly, through the boundary layers or films on each side 01' the engine head. Since all thermal power engines are limited by Carnots efficiency law, the internal temperature of the engine should be the maximum attainable with the materials being used if maximum efficiency is to be obtained. Consequently, the temperature drops across the boundary layers, which are known to be substantial, impose limitations upon the efiiciency of such engines. In addition, substantial heat losses occur as the result of the rte-radiation of heat from such a heated engine head because the relatively slow rate at which the heat energy can be transmitted through the head and particularly the boundary layers. This also adversely atlects the ell'iciency of the engine. Many attempts to improve the transfer of heat energy, from a radiant energy source or other source have been made as can be seen from the aforementioned US. patents. All of these are subject to the same disadvantage however, namely, that the heat energy must be transferred across boundary layers with the attendant temperature drop, and re-radiation losses, and, therefore, subsequent loss in etliciency.

it is an object of this invention to provide a thermodynamic heat engine which avoids the problem of transferring heat energy through a boundary layer.

Another object of this invention is to provide a thermo dynamic heat engine which allows for the transmission of radiant energy directly to the hot space of the engine.

Still another object is to provide a thermodynamic heat engine which operates from solar energy.

Other objects and advantages Will be apparent from the following detailed description which will be given in terms of the embodiment of this invention depicted in FIGURE 2 although the invention is not to be construed as limited thereto.

it has now been found that the objects of this invention can be achieved by providing a thermodynamic reciprocating engine with radiant energy-transparent means which will allow radiant energy to be transmitted directly to the working fluid of the engine where it can be readily converted to heat energy for operating the engine. One embodiment of such an engine incorporating the features of this invention is shown in FIGURE 2 Where 10 is a transparent medium, replacing a portion of the conventional metal engine head 9 of FIGURE 1, which is secured to the cylinder wall by means of ring 12, flange 14 and bolts 13. The transparent medium is chosen so that it does not absorb much visible or infra-red radiation but admits it directly ,to the hot space 3. Although it is not necessary to the functioning of the engine, in

order to achieve a greater efiiciency in absorbing. this radiant energy and converting it into heat energy Within the engine, a matrix of divided black absorbing material is provided at 11.

This matrix can be of wire wool, ceramics, metal grill structures or a thin platinum structure such that it presents a large surface area for maximum absorption of .the radiant energy. Alternatively, such a matrix can be aifixed to the displacer 2 which has the advantage that as the displacer moves within the cylinder 1 it produces a turbulent flow in the Working fluid of the engine and thus more effectively transfers the energy from the matrix to the Working fluid. In cases where the use of such a r fixed matrix may not be desirable, efllcient absorption of the radiant energy can be accomplished by utilizing a radiant energy-absorbing material suspended in the Working fluid such as water vapor in the form of a fog or other material in a very finely divided (cg. colloidal) state, or by utilizing a colored gas such as iodine vapor or nitrogen dioxide as the working fluid.

The transparent medium comprising the engine head can be made of any material which is transparent to is not to be construed as limited to that shown in the accompanying drawing. Because of internal pressure considerations in the engine as well as focusing eiiects it may be advantageous to construct the engine head in a hemispherical form. Other configurations and adaptations, can, of course, also be used. Thus, the radiant energy- -transparent medium can be located in the side walls of an engine head such as is shown in FIGURE 1.

It is to be understood that this invention finds application with energy conversion cycles other than the Stirling cycle. For example, it is as fully applicable using the Rankine cycle or the Ericcson cycle. Furthermore, this invention can be used with any of such engines whether they are being operated on a closed or open cycle.

Thermodynamic engines operating on any of these various cycles and or" many mechanical configurations can be readily adapted to embody the improvement of this invention. Such engines may be of the single-cylinder type or may have a multiplicity of cylinders; they can be of the opposing piston type where the opposing pistons define within a common cylinder a hot space at one end anda cold space at the other end, (with such an engine, the displacer shown in the figures attached hereto can be eliminated); or they can be of the V-type where one segment of the V defines a cold space and the other segment the hot space and where the two segments are joined by a horizontal member containing a regenerator and a radiant energy-absorbing means in association with a radiant energy-transparent medium as hereinbefore defined. Other configurations will of course be evident to those skilled in the art.

Any of such engines, embodying the improvement of this invention, can be readily utilized as a source of electrical power when connected with a generator or alternator. Such systems, particularly with engines employing the Stirling cycle, are eminently suitable as a source of power in space applications. They may also be adapted to function as refrigeration mechanisms, the characteristics of the engine cycles lending themselves readily to such application. I

The least expensive and generally most available source of radiant energy for operating the engines of this invention is the sun. Radiant energy, such as might be obtained from a nuclear reactor or a flame or arc can, however, also be used to supply the motivating energy. Any of such sources can be used with a focusing collector to enhance the supply of energy to the interior of the engine or the transparent medium itself can be constructed in accordance with various lens principles and configurations to accomplish this end.

Having thus described this invention, what is claimed is:

1. A thermodynamic reciprocating heat engine comprising housing means enclosing at least one hot space and at least onecold space, at least one cylinder associated with said hot space and said cold space and containing a power piston operatively connected to mechanical power transmission output means, a Working fluid comprising a primary radiant energy-absorbing means, means connecting said hot space and said cold space to allow said Working fluid to flow therebetween, means separating said hot space from said cold space, secondary radiant energy-absorbing means positioned interiorly of said engine and in association with said hot space and said Working fluid, and an aperture in said engine housing means positioned to allow radiant energy to flow directly into said engine and impinge upon said secondary radiant energy-absorbing means and said working fluid, said aperture being covered by radiant energy-transparent closure means.

2. A thermodynamic reciprocating heat engine according to claim 1 wherein the'radiant energy-transparent closing means is quartz. g

3. A thermodynamic reciprocating heat engine comprising at least one cylinder containing a working fluid comprising a primary radiant energy-absorbing means, a power piston and a displacer piston, said power piston being operatively connected to mechanical power output means and said power piston and displacerpiston defining, within said cylinder, a hot space and a cold space,

said displacer piston separating said hot space from said .cold space, means connecting said hot space and said cold space, secondary radiant energy-absorbing means positioned within said hot space, said cylinder having a cylinder head at least a portion of which is transparent to radiant energy, whereby radiantenergy is allowed to flow directly inthe said hot space and impinge upon said secondary radiant energy-absorbent means and said working fluid. 4. A thermodynamic reciprocating heat engine as claimed in claim 3 wherein the secondary radiant energyabsorbing means in the hot space of the cylinder is aflixed to the displacer.

5. A thermodynamic reciprocating heat engine as claimed in claim3 wherein the radiant energy-transparent portion of the cylinder head is quartz.

References (lites! in the file of this patent 

1. A THERMODYNAMIC RECIPORCATING HEAT ENGINE COMPRISING HOUSING MEANS ENCLOSING AT LEAST ONE HOT SPACE AND AT LEAST ONE COLD SPACE, AT LEAST ONE CYLINDER ASSOCIATED WITH SAID HOT SPACE AND SAID COLD SPACE AND CONTAINING A POWER PISTON OPERATIVELY CONNECTED TO MECHANICAL POWER TRANSMISSION OUTPUT MEANS, A WORKING FLUID COMPRISING A PRIMARY RADIANT ENERGY-ABSORBING MEANS, MEANS CONNECTING SAID HOT SPACE AND SAID COLD SPACE TO ALLOW SAID WORKING FLUID TO FLOW THEREBETWEEN, MEANS SEPARATING SAID HOT SPACE FROM SAID COLD SPACE, SECONDARY RADIANT ENERGY-ABSORBING MEANS POSITIONED INTERIORLY OF SAID ENGINE AND IN ASSOCIATION WITH SAID HOT SPACE AND SAID WORKING FLUID, AND AN APERTURE IN SAID ENGINE HOUSING MEANS POSITIONED TO ALLOW RADIANT ENERGY TO FLOW DIRECTLY INTO SAID ENGINE AND IMPINGE UPON SAID SECONDARY RADIANT ENERGY-ABSORBING MEANS AND SAID WORKING FLUID, SAID APERTURE BEING COVERED BY RADIANT ENERGY-TRANSPARENT CLOSURE MEANS. 